TBILISI, Georgia (AP) -- Georgian prosecutors on Saturday ordered ex-President Mikhail Saakashvili to be questioned over the 2005 death of his prime minister.

Zurab Zhvania's death at a friend's home was ruled accidental and attributed to carbon monoxide poisoning caused by a faulty gas heater. But Zhvania's brother has accused Saakashvili of hiding the truth and called for an investigation.

Saakashvili left Georgia shortly after his second term ended in November and holds a position at Tufts University in the U.S. His spokesman wasn't immediately available for comment.

Georgian prosecutors said they issued a summons to question Saakashvili next week.

Georgia's new prime minister, Irakli Garibashvili, has said if he doesn't attend in person, Saakashvili will be placed on a wanted list. Prosecutors also hope to question Saakashvili in connection with a handful of other cases.

Prosecutors have launched a series of investigations against Saakashvili's allies in recent months. Former Interior Minister Vano Merabishvili was found guilty of embezzlement and abuse of office in February and sentenced to five years in prison.

Merabishvili, who was the interior minister at the time of Zhvania's death and insisted that prime minister's death was accidental, was questioned earlier this week, prosecutors said.

Billionaire Bidzina Ivanishvili routed Saakashvili's party in parliamentary elections in 2012. He stepped down as prime minister late last year but is believed to remain highly influential even without a formal post. Critics said the charges filed against Merabishvili and other Saakashvili allies amounted to political revenge.